i am considering am older schneider-kreuznach symmar convertible lens (150mm/5.6 - 260mm, synchro-compur, serial #5299631) but am unsure if it will give me the quality i need for professional work. was this a coated lens? is there a sacri fice in image quality with a convertible lens design? schneider no longer makes this lens - why? what would be a good price for it? thanks for your comments.